Year 10 Science · Unit 2 · Lesson 16

Chemical Reactions and the Environment

Apply Worksheet

Name

Date

Class

Learning Goals

Trace how ocean acidification can affect coral skeleton growth, then distinguish this pathway from heat-driven coral bleaching.
Compare petrol, ethanol, and hydrogen fuels using evidence from the lesson.
Explain why "zero emission at the exhaust" does not always mean zero carbon overall.

Warm Up

Because… chain

Each row on the left is one step, and the next row is what happens after it. In the box, write the because — the reason that step forces the next one. Do not copy the next step’s words back; explain what makes it follow.

Fossil fuels burn and add CO₂ to the atmosphere

→

Some CO₂ dissolves in seawater and changes its carbonate chemistry

→

Ocean pH falls and carbonate ions become less available

→

Corals and other calcifiers may build calcium-carbonate skeletons more slowly

→

Reef-building may slow and reef structures can weaken over time

→

These changes can add stress to reef ecosystems

A separate pathway: unusually warm water causes heat stress and can make corals expel their symbiotic algae (bleaching). Acidification and warming can occur together and compound reef stress, but they affect corals through different processes.

Overall outcome:

Your Turn

Real-world context

Australia is exploring alternatives to petrol-powered transport. Queensland already blends 10% ethanol (E10) into petrol at the pump, sourced mainly from sugarcane grown in North Queensland. Several Australian states are investing in hydrogen refuelling infrastructure, while the CSIRO is developing hydrogen technology for domestic and export use. In 2023, there were approximately 20,000 electric vehicles on Australian roads, but hydrogen fuel cell vehicles remain rare.

(a) Compare petrol and sugarcane ethanol as transport fuels. Your answer should address CO₂ emissions and net carbon footprint for each fuel. Use chemical equations or word equations to support your comparison.

Apply 3 marks

(b) Hydrogen fuel cells produce only water vapour. Explain why hydrogen from natural gas (steam methane reforming) is NOT truly zero-carbon, even though the vehicle itself emits no CO₂.

Apply 2 marks

Wrap Up

In one sentence, explain why the source of a fuel matters just as much as what the fuel produces when it burns.